查看更多>>摘要：The proposition of ratiometric detection mode has demonstrated great superiority in improving analysis accuracy by forming self-calibration. Herein, the novel dual-reverse-signal ratiometric fluorescence detection for malachite green (MG) was first achieved based on synergistic effect of fluorescence reso-nance energy transfer (FRET) and inner filter effect (IFE). The ratiometric fluorescence probe (B-RCDs) was self-assembled via electrostatic attraction between blue-emission carbon dots (BCDs) and red-emission carbon dots (RCDs), followed with FRET effect from BCDs to RCDs and exhibited dual -emission at 450 nm and 627 nm. In the presence of MG, the IFE effect between MG and RCDs quenched the fluorescence at 627 nm and restored the fluorescence at 450 nm, sending out two reverse signals along with an obvious color change from pink to purple (302 nm UV lamp). This ratiometric method not only simplified the preparation process, but also improved the detection sensitivity, showing a low limit of detection (LOD) of 41.8 nM, which exhibited superiority than that of single-signal RCDs (157.3 nM). This method held a rapid response of 10 min and represented satisfactory recoveries (99.14%-109.08%) in real water samples, revealing it was a promising candidate in the fast, sensitive and practical detection of MG. Moreover, the design of synergistic effect supplied a new perspective for the development of ratiometric sensing in the future.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Cosputtering technology was utilized to prepare a Ag and indium tin oxide (ITO) composite on a flat polystyrene (PS) microsphere array. The carrier density estimated by Hall effect testing of different Sn concentrations in the cosputtered films can be tuned from 10(18) to 10(20) cm(-3). The bandgap calculated based on ultraviolet photoelectron spectroscopy can be adjusted within the range of 3.95-4.02 eV. We explored the possible mechanism of charge transfer (CT) by varying the bandgap and explained the causes of the surface-enhanced Raman scattering (SERS). Surprisingly, a synchronous change in the CT process with the carrier density was discovered. This observation suggests that the CT process can be precisely regulated by changes in the composition of the metal-semiconductor nanostructures. Our study provides a reference for the application of Ag/ITO films as alternative near-infrared plasmonic materials. (C) 2022 Elsevier B.V. All rights reserved.
Toledo, Luiz F. R. B.Turchetti, Denis A.Glislere, Ana P.Nowacki, Bruno...
9页
查看更多>>摘要：The rationale of this paper is to shed some light on the origin of the optical response of two similar chiral fluorene copolymers in correlation with their vibrational modes, to understand how a chiral center placed in a ramification affects the optical properties of the main chain. Various spectroscopic ellipsometric techniques, in the scope of the Stokes theory were used to characterize the optical-vibrational behavior of the polyfluorenes: ellipsometry in emission (EE), transmission (TE), and Raman (ERS). The results showed that the optical activity and the emission of the circularly polarized light depends substantially on the interaction of the chiral carbon in the ramification and the main chain through specific optically active vibrational modes, for each sample. One interesting achievement was to find the absolute dextrorotatory configuration of the studied molecules, that could induce a helicoidal structure to the entire material. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A novel dual-functional peptide probe FLH based on fluorescent "on-off-on " strategy and colorimetric visualization method was designed and synthesized. This new probe exhibited highly selective and rapid detection of Cu2+ with significant fluorescent "turn-off " response, with a visible colorimetric change from yellow to orange. The combination ratio of FLH to Cu2+ (1:1) was determined using ESI-HRMS spectra and Job's plot. The fluorescent emission showed a good linear response (R-2 = 0.9986) with a low detection limit of 1.5 nM. In addition, the FLH-Cu(2+ )complex displayed colorimetric changes and a fluorescent "off-on " response toward CN- over a wide pH range from 7 to 12. This detection behavior was observed within 20 s, with a limit of detection (LOD) for CN- at 12.7 nM. Based on stability and accuracy, FLH was next developed as dual-functional test strips, and was also successfully applied to detect Cu2+ and CN- in two actual water samples. More importantly, the cytotoxicity studies indicated that FLH had good biocompatibility and low toxicity, and was successfully utilized for monitoring Cu2+ and CN- in living cells through fluorescence imaging. (C) 2022 Elsevier B.V. All rights reserved.
Kim, GyeongjinGil, DongkyunLee, Jae JunKim, Jiwon...
11页
查看更多>>摘要：A novel 7-nitro-1,2,3-benzoxadiazole (NBD)-based chemosensor BOP ((5-bromopyridin-2-yl)(4-(7-nitro benzo[c][1,2,5]oxadiazol-4-yl)piperazin-1-yl)methanone) was synthesized. BOP could detect S(2-)through fluorescent quenching and colorimetric change. The detection limit was calculated to be 10.9 lM through fluorescence titration. The reaction mechanism of BOP towards S(2-)was estimated to be thiolysis of NBD amine, producing the cleavage products, NBD-S- and BP ((5-bromopyridin-2-yl)(piperazin-1-yl)metha none). The thiolysis was demonstrated by H-1 NMR titrations, ESI-mass analysis and theoretical calculations. Importantly, BOP was able to successfully monitor S(2-& nbsp;)in zebrafish and water samples. Additionally, test strips coated with BOP were applied to the in-the-field measurements of S2-. (c) 2022 Elsevier B.V. All rights reserved.
Radwan, Aya SaadElkhoudary, Mahmoud M.Hadad, Ghada M.Belal, Fathalla...
7页
查看更多>>摘要：Allergic rhinitis and urticaria are extremely prevalent among all age groups. From the clinical experience, usually, an essential second-generation non-sedating H-1-antihistaminic drug, such as bilastine is given to relieve allergic symptoms. Bilastine is preferred to be used instead of oral corticosteroids and first generation sedating H1-antihistaminics to avoid their side effects.A highly sensitive and simple spectrofluorometric method was developed and validated for the determination of bilastine in its dosage forms and biological fluids. The quantum yield was calculated and was found to be as high as 0.48. Aqueous water solution of bilastine gives high native fluorescence emission at 298 nm after excitation at 272 nm. A rectilinear calibration plot was obtained over the concentration range of 1.0-50.0 ng mL(-1). The limits of quantitation and detection were 1.0 and 0.33 ng mL(-1), respectively. The parameters influencing its spectrofluorimetric behavior, viz, type of solvent, pH and organized media were studied.The proposed method was successfully applied for the determination of the drug in pharmaceutical dosage form and the results obtained were in good agreement with those of given by reported method. The high sensitivity of the proposed method enabled the estimation of the drug in biological matrices, including human plasma and urine samples after simple protein precipitation, and the results obtained were satisfactory. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Rapid, robust, and accurate biomass compositional analyses are required in the bioenergy industry to accurately determine the chemical composition of biomass feedstocks. A stacked regression ensemble approach using near infrared spectroscopic method was developed for the quantitative determination of glucan, xylan, lignin, ash, and extract in biomass feedstocks. A comprehensive comparison of the performance of various machine learning techniques including support vector regression (linear and radial), least absolute shrinkage and selection operator (LASSO), ridge regression, elastic net, partial least squares, random forests, recursive partitioning and regression trees, gradient boosting, and gaussian process regression was assessed in the training set data (n = 188). The predictive performance of the aforementioned machine learning approaches was then compared with stacked regression, an ensemble learning algorithm which collates the performance of the abovementioned machine learning regression techniques. Results show that the stacked regression primarily outperformed other machine learning techniques (Root mean square error of prediction (RMSEP)average = 1.660%wt; R-2 = 0.907) across all five constituents in the validation set data (n = 81). Further results also show that the RMSEP of the stacked ensemble technique is significantly different than that of the partial least squares (PLS) approach in predicting glucan, ash, lignin, and extract components in biomass samples. The stacked ensemble learning approach offers an alternative method for a more accurate prediction of biomass compositions than the traditional PLS technique. (C)2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The electronic structure and related optical properties of the nitroprusside ion, [Fe(CN)(5)NO](2-) , are dominated by the nitrosyl (NO') group. The light-induced 2b(2)(xy)-. 7e(pi*NO) (Fe -> NO) and related appearance of meta-stable isomers for the NO group supports many of the functional properties of metal nitroprussides. In recent studies on the preparation of 2D transition metal nitroprussides from their 3D analogs, we have observed that such a structural change is concomitant with a decrease for the v (NO) frequency and certain band splitting (unfolding). The 3D to 2D structural modification leads to an increase in the electron density at the iron atom. This results in an enhancement for the pi*-back donation, which increases the electron population at the pi*2px and pi*2py orbitals. These last orbitals are doubly degenerated, and the increase for the pi*-back bonding induces the removal of that degeneration via the Jahn-Teller effect. This intuitive mechanism explains the mentioned band unfolding related to the structural change. Such explanation was herein supported by a model based on the normal modes for the FeNO fragment derived from the small oscillation formalism around the equilibrium positions for the involved atoms. This model shows that there is a very close relationship between the deformation of the nitrosyl group (NO') and the splitting of the IR bands. That is, the less linear the nitrosyl group, the greater the shift and splitting of the mentioned IR band. An excellent coincidence between the frequency values calculated using the model and the experimental ones was observed. The largest difference between the theoretically calculated v(NO) frequencies and the experimental ones was only 6 cm(-1) and 5 cm(-1) in representative samples of 2D and 3D transition metal nitroprussides, respectively. The understanding of such an effect could be relevant for the functional properties of these 2D coordination polymers. (C) 2022 Elsevier B.V. All rights reserved.
Nicolas, Mari F.Marin, Jayr H.Paganoto, Giordano T.Fernandes, Rafaella F....
8页
查看更多>>摘要：This study shows a new SERS (Surface-enhanced Raman Scattering) and SEF (Surface-enhanced Fluorescence) platform approach, in which substrates were constructed from the silver nanoparticles stabilized by alginate polymer (AgALG) and encapsulated in hydrogel calcium alginate beads (AgALGbead). In this regard, the electrostatic repulsion or attraction concerning the charged dyes and the carboxylate groups of the alginate could define the distances between the probe molecules and metallic nanoparticles to determine the SERS or SEF effect. In this sense, the anionic dye named New Indocyanine Green (IR-820) and the cationic dye Rhodamine 6G (Rh6G) were selected to discuss the alginate's ability to quench or enhance the fluorescence and the Raman dyes signals. Furthermore, the SEF effect using the IR-820 dye can be detected for the near-infrared emission (S-1 -> S-0) using the 532 and 633 nm laser lines as well at the visible region (S-2 -> S-0) applying the excitation at 532 nm in the AgALGbead substrates. Nevertheless, the cationic dye provides the Surface-enhanced Resonance Raman Scattering (SERRS) effect and quenching of the fluorescence for the same AgALGbeads substrate at 532 nm laser line. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Fluorescent carbon dots (CDs) with the long-wavelength emission have received increasing attention due to their promising application prospects in the biological field. The synthesis of CDs with long wavelength emission mainly focuses on the high temperature method, but the room temperature synthesis is still rarely studied. Herein, a simple room temperature strategy is developed for the preparation of orangeemitting CDs (O-CDs) by Schiff base crosslinking reaction between methyl-p-benzoquinone and triethylenetetramine. The proposed O-CDs show a strong excitation-dependent emission with a relative quantum yield of about 6.56%. Because of the strong inner filter effect, O-CDs can be well applied for the highly-sensitive detection of vitamin B12 (VB12). The intensity ratio (F/F0) of O-CDs is linear against the concentration of VB12 from 50 nM to 200 lM with a low detection limit of 10 nM. Therefore, the obtained O-CDs nanoprobes provide a promising platform for pharmaceutical analysis applications. (c) 2022 Elsevier B.V. All rights reserved.
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